The key contribution of electron microscopy methods to condensed
matter spectroscopy is undoubtedly spatial resolution. So far this has
mainly been manifest through electron energy loss spectroscopy in the
1-eV to 10-keV energy range and has not seriously challenged the
dominance of optical, X-ray, and neutron spectroscopy methods over most
of the vast field at lower energies. At frequencies up to a few
megahertz, corresponding to energies of a few nanoelectron volts and
below, direct excitation by pulsed electron beams or electric fields
has proved effective. Prospects are discussed for extending spatially
resolved spectroscopy to the intermediate energy region, mainly by
combining the advantages of electrons with those of photons.